Console Input of strings using Scanner question

[David A King]

I am having a great deal of frustration trying to use the scanner to get user input from the eclipse console.
Here is what I am trying to do.
Print a menu for the user with options, take that (1) char input and run it into a switch statement for processing.
I have that done and it is working fine.

If the user chooses to enter strings for storage, They are instructed to enter their string and press enter to complete that string entry.
Then enter the next string and press enter, etc.
So I have a While loop for this. Get the scanner input, store it in the LinkedList, get the next scanner input, etc.
I get the scanner string and store it in a Linked list. That works fine.
The user is instructed to simply enter a blank string to end the entry procedure, like just press Enter on the new line without typing a new string.
The problem is the scanner doesn't seem to return anything for me to Test to close this procedure.
How do I TRAP the fact that the user just pressed enter so I can end my procedure?
I have tried next() and nextLine() and reset(), etc. And I am getting knowhere.

Thanks,

*Dave

[Liutauras Vilda]

Hi David,

Maybe just post what you got so far and someone will help.

[David A King]

import java.util.Scanner;
import java.util.*;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.lang.reflect.InvocationTargetException;

public class Proj15IO {
	char uChoice;
	String usrInput;
	Scanner usrConsole = new Scanner(System.in);
public 	List<String> usrStrIn;

	static int e = 0; // switch value for Entered char


public static void main(String [] args){
	
	Proj15IO testProj = new Proj15IO();
	
	testProj.printMenu();
	testProj.checkEntry();
	if(e < 4) {
	testProj.actions();
	}else testProj.printMenu();
	
	
	
}

	public void printMenu(){
		System.out.println("Please enter a letter from the menu and press Enter.");
		System.out.println("=======================================================");
		System.out.println("  (e)nter text\t(s)ave text\t(r)ead text\t(q)uit");
		System.out.println("=======================================================\n");
		System.out.println("Your choice : ");
		uChoice = usrConsole.next().charAt(0);
		System.out.println("You entered an : " + uChoice);
		
	}
	
	public void actions(){
		boolean state = true; // do-while loop control flag
		switch (e) {
		case 0:
		{
			System.out.println("You chose to enter text, enter your text and press enter after each entry.\n");
			System.out.println("enter a blank string to End text entry mode.\n");
			List<String> usrStrIn = new LinkedList<String>();
			
			do
			{
			
			usrInput = usrConsole.next();
			System.out.println("I got it:"); // debug print to see scanner returned value
			
			if(usrInput.length() > 1){
			usrStrIn.add(usrInput); // add string to LinkedList
			}else
				if(usrInput.length() < 1){
				state = false;
			}
			
			}while(state);
				
			System.out.println("\nYou chose to STOP entering text strings.\n");
			printMenu();
			break;
		}
			
		case 1:
			break;
		case 2:
			break;
		case 3:
		{   // user chose to exit the program
			System.out.println("You chose to Quit the Program. ");
			System.exit(0);
		}
		}
  	}
	
	public int checkEntry(){
		if (uChoice == 'e' || uChoice == 's' || uChoice == 'r' || uChoice == 'q'){
			if(uChoice == 'e')
				e = 0;
			else
			  if( uChoice == 's')
					e = 1;
			else
			  if( uChoice == 'r')
						e = 2;
			else
			  if(uChoice == 'q'){
							e = 3;
			  }
			return e;
		}else
			{
			System.out.println("*Error*\n Please Enter only a (e s r q)  as menu choices\n");
			e = 4;
			}
		return e;
	}	
}

[Campbell Ritchie]

Scanner??? Yesyesyesyes.
Scanner.nextChar??? Nonononononono.

At this point you start getting confused. You would like to use a Scanner#nextChar method but there is no such thing, even though there seem to be lots of Scanner#nextXXX methods. I think the idea was that a Scanner divides input into “tokens” and you can't necessarily have a char as a token. The nearest you can get to that is to use myScanner.next() to get the next token and then it is a String. Remember Strings have a method which gives you the char at a particular location. Remember that String indices are related to array indices, so they start at 0. Unless you do something silly with your Scanner, you cannot get an empty String from Scanner#next, so every token you get will have a “first” character.

[Campbell Ritchie]

A few minutes ago, I wrote: . . . you cannot get an empty String from Scanner#next . . .

You can however get an empty String with Scanner#nextLine, so if you ever have problems with nextLine do ask. I know the solution.